1. Field of the Invention
This invention relates to a new method of making planarizing layers for superconducting and for semiconductor devices. More particularly, this invention relates to a method of vacuum depositing a layer of conductive metal which is made laterally non-conductive while retaining its conductivity in the vertical direction.
2. Description of the Prior Art
Layers of conducting and insulating materials are built up on a substrate when making a semiconductor device. Some of the layers are formed as distinct patterns. Each vacuum deposited layer formed over a pattern is substantially uniform in thickness and follows the contour of the previous patterned layers. As a result, the subsequently vacuum deposited layer becomes substantially thinner at the edge of a raised pattern than at its adjacent area. This weakened area or portion is called a step and is known to cause device failures during the process of manufacturing of semiconductor and superconducting devices. The step or weakened area is also known to cause device failures of devices which have passed manufacturing acceptance test. Thermal cycling and stress concentrations at the weakened area result in such delayed failures.
The weakened step area is most pronounced when the base electrode of a Josephson junction device is formed on a substrate and then substantially isolated by a layer of insulating material such as silicon dioxide which is formed over the base electrode area. In my copending application, Ser. No. 362,578 filed Mar. 26, 1982, a method of eliminating the harshness of the insulating layer step in the Josephson junction device is described. In this copending application, the insulating layer is formed by two separate and distinct deposition steps combined with a known step of forming the base electrode.
It is known that some single crystal compounds exhibit anisotropy in their electrical conductivity properties (the conductivity is higher in one direction than in the other directions). Heretofore, there was no conducting or superconducting metal known to be vacuum deposited so that it exhibited gross electrical anisotropy.
It would be desirable to provide a novel electrical anisotropic planarizing layer of conductive metal for use in the manufacture of superconducting devices and semiconducting devices.